Probing Long-Lived Plasmonic-Generated Charges in TiO2/Au by High-Resolution X-ray Absorption Spectroscopy

Exploiting plasmonic Au nanoparticles to sensitize TiO2 to visible light is a widely employed route to produce efficient photocatalysts. However, a description of the atomic and electronic structure of the semiconductor sites in which charges are injected is still not available. Such a description is of great importance in understanding the underlying physical mechanisms and to improve the design of catalysts with enhanced photoactivity. We investigated changes in the local electronic structure of Ti in pure and N‐doped nanostructured TiO2 loaded with Au nanoparticles during continuous selective excitation of the Au localized surface plasmon resonance with X‐ray absorption spectroscopy (XAS) and resonant inelastic X‐ray scattering (RIXS). Spectral variations strongly support the presence of long‐lived charges localized on Ti states at the semiconductor surface, giving rise to new laser‐induced low‐coordinated Ti sites. Hot electrons: An atomistic description of the electronic and structural changes of TiO2 resulting from the injection of hot electrons is presented. High resolution X‐ray spectroscopy shows that plasmonic charges are trapped on Ti states at the semiconductor surface, giving rise to transient low‐coordinate Ti sites which have long‐enough lifetimes to play a major role in catalytic processes (LSPR=localized surface plasmon resonance).